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¡2 FocusingandDepthofField
The focusing of wide-angle lenses appears to be relatively non-critical due
to their large depth of eld However, careful focusing is actually necessary
to utilize the high imaging quality of this lens to the full To ensure maxi-
mum brightness of the focusing screen and the best recognition of the ide-
al focusing point, the aperture should be opened by pivoting the stopping-
down lever toward the shifting knob The aperture setting ring therefore
remains on the set working aperture so that the aperture can later again
be closed to the working aperture quickly using the stopping-down lever
directly before the shot without moving the eye from the viewnder
Focusing can generally take place before or after the parallel shift as de-
sired However, if the LED focus display of an autofocus camera is used for
manually focusing, focusing must take place in the centered position (ie
with a non-shifted lens) because the AF sensor requires incidence of light
approximately parallel to the axis, but the light is obliquely incident on the
sensor when the lens is shifted The parallel shift which then takes place
after the focusing does not inuence the set distance
The f-numbers at both sides of the index mark for distance and aperture
indicate the depth of eld: If eg everything from ¡ m to 3 m should be
sharp, the distance ring should be set so that the meter gures ¡ and 3 are
above the same f-number (here: 8) at both sides of the index mark